The Upper Cretaceous through Paleocene interval is characterized by dramatic shifts in climate and by the K-T extinction and Paleocene radiation. The climatic variations are an invaluable context for understanding transitions into and out of greenhouse climates, the relationships and/or lags between marine and terrestrial records, and patterns of ocean circulation. Highly resolved time scales of climate and biotic changes in this interval will be essential for understanding the geographic variations in climate perturbations in both terrestrial and marine sections and how biology responds.
Dr. Johnson collaborates with Sam Bowring at MIT and Will Clyde at the University of New Hampshire to oversee an integrated program of magnetostratigraphy, palynostratigraphy, and U-Pb geochronology of volcanic ash beds interlayered with fossil-bearing rocks that will result in geochronological tie-points determined to better than 0.1 percent uncertainty and greatly improve derivative age models for the time period between 70 and 55 million years ago. This is the first attempt to use U-Pb geochronology to calibrate this interval of time, which has traditionally relied on 40Ar/39Ar geochronology. This project is funded by the National Science Foundation (SGP-642838).
